Analysis of Micelle Formation and Adsorption Layers of Binary Mixtures of Sulphate Soap Components

Abstract

Currently, the main trend of the pulp and paper industry development is bio-refining. It is based on integrated and deep processing of wood raw materials to obtain products with higher value added and reduced amount of waste. One of the high priority tasks of bio-refining is improvement of technology of by-product (sulphate soap) extraction from spent liquor with an increase in the yield and quality of the resulting product and a decrease in the level of environmental pollution. The complexity and energy intensity of sulphate soap extraction from spent liquor depends on many factors, including the species used for wood cooking, composition of extractives, the method of wood preparation for delignification, etc. Sulphate soap is a multicomponent emulsion with a predominant content of resin and fatty acids, small amount of unsaponifiable substances and an admixture of lignin, which is mainly extracted from waste liquior by settling. The low degree of its extraction is associated with the absence of systematical data on the mutual influence of the sulphate soap components. In this work, the patterns of intermolecular interaction of the individual components of the by-product (sulphate soap) are found. For this purposes the critical concentration of micelle formation (CCM) and surface tension depression of surface-active sodium oleate and sodium abietate and their mixtures of varying compositions were determined by the methods of tensiometry and conductometry. A detailed analysis of its mixed micelles and adsorption layers was carried out using the Rubin–Rosen pseudophase model. The interaction mechanisms of components in mixtures are explained. The impact on the composition of micelles and adsorption layers of the more surface-active sodium oleate was detected in mixed solutions. A maximum synergistic effect of micelle formation was observed in mixtures with a predominant content of sodium abietate. Analysis of experimental data and the result of sulphate soap modeling allow substantiating the complexity of its extraction from waste liquor after wood cooking with the presence of hardwood over 30 %, which is explained by the reduced content of resin acids in black liquor. For citation: Yakubova O.S., Demiantseva E.Yu., Smit R.A., Dubovy V.K. Analysis of Micelle Formation and Adsorption Layers of Binary Mixtures of Sulphate Soap Components. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 196–205. DOI: 10.37482/0536-1036-2021-6-196-205